Plastic closure device for tubular bags

ABSTRACT

A plastic closure device ( 1 ) with a lower part ( 2 ) is disclosed which can be fastened in a non-releasable and integrally bonded manner by means of ultrasonic welding to a plastic film or a plastic patch. A flange ( 20 ) of the lower part ( 2 ) is connected by an underside thereof to the plastic layer in an integrally bonded manner by means of introducing ultrasonic energy of a sonotrode into the flange ( 20 ). An energy-introducing arrangement, comprising a plurality of energy-introducing ribs ( 23 ), is used to introduce the ultrasonic energy into the flange ( 20 ), as a result of which the weld parts are welded under the action of a static joining force. Owing to the design according to the invention of the energy-introducing arrangement, a desired connection can be achieved in spite of a reduced static joining force, a reduced ultrasonic energy and, in general, with the use of a reduced welding power by comparison with prior art methods.

BACKGROUND OF THE INVENTION

The present invention describes a plastic closure device for tubularbags, having a bottom part, comprising a discharge outlet and a flangehaving a flange bottom side on which there is disposed anenergy-introducing arrangement which can be connected to a plastic layerby means of ultrasonic welding.

Plastic closure devices for tubular bags, which in technical languageare generally referred to as pouches, are known in differentembodiments.

The plastic closure devices generally comprise a bottom part, fasteneddirectly on the tubular bag, and a screw cap, releasably fastenable onthe bottom part, for closing off a discharge outlet in the bottom part.For the fastening of the plastic closure device, a flange of the bottompart is fastened on the plastic film material of the tubular bag in anon-releasable, integral manner by ultrasonic welding. This welded jointis realized either directly between the flange bottom side and theplastic film of the tubular bag, or between the flange bottom side and aplastic patch which closes a punched opening in the plastic film of thetubular bag.

As is made clear in the diagrams according to the prior art, theultrasonic welding of plastic in the region of a joining zone of theflange as the weldment by means of a sonotrode leads to thenon-releasable connection of the flange to the tubular bag or theplastic patch. In order that a static joining force can be appliedperpendicularly to the flange, the sonotrode is pressed with a definedjoining force against a so-called anvil. This anvil is not representedin the figures.

In order to achieve a sufficiently firm and liquid-tight connectionbetween the bottom side of the flange and the tubular bag, according tothe prior art an energy-introducing rib, which runs all the way roundthe flange, has been disposed on the bottom side of the flange.According to the appended figure, an energy-introducing rib which is asblunt as possible and points with a flat face in the direction of thetubular bag and which withstands the high static joining forces that arenecessary for optimal welding, has been provided. The energy-introducingrib is made as blunt as possible with sufficient thickness, so that thestatic joining force can be evenly applied to as large a surface area aspossible.

The mechanical ultrasonic vibrations are transferred under pressure tothe flange in the region of the energy-introducing rib, wherein, bymolecular and boundary friction, the heat which is necessary for theplasticization of necessary heat is generated on the basis of pressurethreshold loading and an approximately homogeneous welding of thesurface of the energy-conducting rib in a large region ensues, in thatthe blunt energy-conducting rib is plasticized and provides a large-areaconnection.

The method according to the prior art delivers satisfactory results withlow welding times, wherein, due to the thickness of theenergy-introducing rib, a liquid-tight, large-area welding is achieved.The efficiency of the fastening method is open to improvement, however,since a total power of several thousand Watts for the entire connectingoperation by ultrasonic welding is necessary in order to achieve thedesired liquid-tight, non-releasable connections. According to the priorart, the necessary static joining force in respect of film thicknessesof, say, 125 μm, is about 400 N and must be applied, as far as possible,perpendicularly to the flange surface. Integral connections between theplastic closure device and the plastic film are thereby achievable insuch strength that the connection withstands tensile forces of about 0.2to 0.5 N/mm2.

Depending on the application and loading of the tubular bag, thisachievable strength is insufficient. In order to create an optimalplasticization of the energy-introducing ribs and hence a sufficientlystrong connections, a structured anvil was used. The drawback of astructured anvil is the possibility that bacteria will hide in thestructured surface, or that the structure of the anvil will damage theplastic film of the tubular bag, including next to the welding point.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a plastic closuredevice which, in comparison to known plastic closure devices known fromthe prior art, can be fastened on the tubular bags by means of lowerstatic joining forces, lower amplitudes, lower welding energies, andthus, in total, by means of lower welding powers. Due to the highquantities, a more cost-effective fastening of each individual plasticclosure devices leads to enormous savings worldwide in the region ofbillions of dollars per annum.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred illustrative embodiment of the subject of the invention isdescribed below in connection with the appended drawings.

FIG. 1 shows a perspective view of a two-part plastic closure device,while

FIG. 2 shows a view of the bottom side of the bottom part with theinventive energy-introducing arrangement.

FIG. 3 shows a longitudinal section through a plastic closure devicewith mounted sonotrode, while

FIG. 4 shows a sectional view of a detail of the flange in the region ofthe joining zone.

FIG. 5 a shows a diametrical vertical section through a bottom part,wherein the flange, in the outer marginal region after the outerenergy-introducing rib, is of rounded construction, while

FIG. 5 b shows a section through a bottom part along the sectional lineW-W according to FIG. 2.

FIGS. 6 a and 6 b show a plastic closure device according to the priorart.

DETAILED DESCRIPTION

The inventive plastic closure device is denoted in its entirety by 1 andcomprises a bottom part 2 onto which a screw cap 3 can be releasablyfastened to form a seal. Optionally, the screw cap 3 can be fastened tothe bottom part 2 by a guarantee band 4 as protection against prioropening, so that an intact guarantee band 4 is a sign of a plasticclosure device 1 which has never previously been opened. The bottom part2 comprises a normally cylindrically shaped discharge outlet 22, on theouter face of which is arranged an external thread 21 and which isdelimited by a flange 20. The screw cap 3 has an internal thread (notrepresented), which can be brought into operative connection with theexternal thread 21, whereby the plastic closure device 1 can be closedin a liquid-tight manner.

The bottom part 2 can also be provided with a hinged cap, or a piercingelement disposed in the bottom part 2. It is only important that theplastic closure device 1 should have a bottom part 2 with dischargeoutlet 22 and a peripheral flange 20.

With the flange 20, the bottom part 2 can be fastened directly orindirectly to a plastic film 5, as shown in detailed representation inFIG. 3, wherein the plastic film 5 constitutes a part of a tubular bag(not represented). Depending on use, the tubular bag can be filled withdifferent liquids, wherein the liquid can be extracted from thedischarge outlet 22 from the tubular bag following the removal of thecap. The opening in the tubular bag which is necessary beneath thedischarge outlet 22 can be produced either by a corresponding device tothe abovementioned piercing element, for instance, or can be madedirectly in the plastic film 5 of the tubular bag.

The bottom side 200 of the flange 20, which is facing away from the cap3, for instance a screw cap 3, has an energy-introducing arrangement inthe form of a plurality of energy-introducing ribs 23, which skirt theround flange 20 and project away from the bottom side 200 of the flange20. The energy-introducing ribs 23 are here preferably at leastapproximately parallel to one another and are arranged at such adistance from the inner diameter of the flange 20 or of the dischargeoutlet 22 that they lie outside the region of the cap 3.

A non-releasable connection of the bottom part 2 to the plastic film 5of the tubular bag is effected by means of ultrasonic welding. After thebottom part 2 has been placed with the bottom side 200 of the flange 20on the plastic film 5, a sonotrode 6, which is usually of rotationallysymmetric configuration, is positioned on the flange top side 201, whichis facing away from the energy-introducing ribs 23. The sonotrode 6 isadvantageously configured as a rotary sonotrode 6, which has a receivingspace 60 into which the bottom part 2, where necessary with mounted cap3, can be received, while the bearing edge 61 of the sonotrode 6 hasdirect contact with the flange top side 201. The ultrasonic energy isintroduced into the region of the joining zone Z at least approximatelyperpendicularly to the flange top side 201, wherein the vibrationaldirection S of the sonotrode 6 is realized, say, longitudinally roughlyparallel to the longitudinal axis of the bottom part 2 of the plasticclosure device 1. With an amplitude A, high-frequency mechanicalvibrations, generated by a connected generator, are realized, whichvibrations correspond to the working frequency of the sonotrode 6.

During the introduction of the mechanical ultrasonic vibrations, astatic joining force F is applied at least approximately perpendicularlyto the flange top side 201 during a welding time. The static joiningforce F points roughly in the vibrational direction S. The sonotrode 6presses the bottom part 2 under the static joining force F against ananvil (not represented).

As a result of the high-frequency ultrasonic vibration, the contactpoints between the plastic film 5 and the flange 20 is or are heated,whereby the integral connection between the bottom part 2 and thetubular bag or plastic film 5 ensues. The welded joint can be realizedeither directly between the flange bottom side 200 and the plastic film5 of the tubular bag, or between the flange bottom side 200 and aplastic patch inside the tubular bag beneath the plastic film 5 of thetubular bag, wherein the ultrasonic vibration correspondingly introducesenergy into the energy-introducing ribs 23.

After the actual welding operation also, the joining force F persistsfor a dwell time, wherein the flange 20 and the plastic film 5 coolsunder pressure.

Tests have shown that the plurality of energy-introducing ribs 23 shouldbe arranged over a width b on the bottom side 200, wherein the flangetop side 201, spanning the width b, should be fully covered during thewelding operation by the bearing surface, here the edge 61 of thesonotrode 6, in order to ensure an optimal energy input. Theenergy-introducing ribs 23 should be arranged approximately parallel ata distance apart b′, wherein the energy-introducing ribs 23 and theflange bottom side 200 are distanced by a height h from the plastic film5.

Tests have shown that two or more, preferably three, energy-introducingribs 23 over the width b lead to optimal liquid-tight welded joints. Incomparison to methods according to the prior art, the static joiningforce F which is to be expended, and the overall expended power, wasable to be reduced, wherein welded joints of equivalent quality areachievable.

The height h is determined by the distance between the flange bottomside 200 and the elevation maximum of the energy-introducing ribs 23,and thus by the plastic film 5 which is to be welded on. Heights h of0.2 to 0.4 mm were chosen. The energy-introducing ribs 23, which incross section are configured rounded into their end, have a radius r of0.1 to 0.3 mm. The elevation maxima of the energy-introducing ribs 23 inthe form of domes give rise, viewed in cross section, to roughlypunctiform bearing surfaces against the plastic film 5. The flanks ofthe energy-introducing ribs 23 enclose an angle α between 50° and 70°,preferably of 60°. The domes of the energy-introducing ribs 23 liebeneath the flange bottom side 200 on circular bearing lines or narrowbearing surfaces.

The distance apart b′ of adjacent energy-introducing ribs 23 of theenergy-introducing arrangement is chosen between 1 mm and 1.5 mm,depending on the flange width B and width of the bearing edge 61 of thesonotrode 6, so that, in the case of three parallel, and thusnon-intersecting energy-introducing ribs 23, the width b of theenergy-introducing arrangement is about 2.5 to 2.7 mm. Since threadflanks of the external thread 21 project partially over the flange topside 201, the bearing edge 61 of the sonotrode 6 can usually be mountedonto the flange top side 201 such that it does not bear against thedischarge outlet. It is important, however, that the edge 61 rests asflatly as possible on the flange top side 201, lying opposite theenergy-introducing arrangement on the flange bottom side 200, whereinthe ultrasonic energy can be optimally introduced by the sonotrode 6into the flange 20 and the energy-introducing ribs 23. In order toachieve a largest possible region of energy transfer to the flange 20,the sonotrode 6 must be led as closely as possible past the threadflanks of the external thread 21, so that a maximal contact surface onthe flange top side 201 is covered.

Example

In series of tests which have compared the welding method according tothe prior art, where only one energy-introducing rib is used, with theuse of a plastic closure device 1 having a plurality ofenergy-introducing ribs, a significant reduction in the necessary staticjoining force F, and, above all, in the maximally necessary power, wasable to be measured. Here good results were manifested with the use ofenergy-introducing arrangements comprising two and threeenergy-introducing ribs 23, wherein the best results were able to beachieved with three energy-introducing ribs 23.

The weld fastening of a bottom part of a plastic closure deviceaccording to the prior art is compared with a bottom part 2 with specialenergy-introducing arrangement comprising three energy-introducing ribs23 on identical plastic films 5 each having a thickness of 5 mil, whichcorresponds to a thickness of (1 mil=25.4 μm) about 125 μm. The surfaceareas of the flange bottom sides 200 and flange top sides 201 of theknown bottom part, as well as of the novel bottom part 2, wereidentical, so that the results are comparable.

In the case of more than three energy-introducing ribs, these must bereduced in thickness so as not to add further to the energy and powerrequirement. As a consequence, the volume of the material necessary forthe welding would be too low, however, and the strength of the weldedjoint would be reduced.

Table 1 shows the direct comparison of the method parameters forfastening the known bottom part and the novel bottom part 2respectively.

TABLE 1 Prior art Invention Welding time 0.160 s 0.200 s Dwell time0.100 s 0.100 s Amplitude A 95% 90% Static joining force F 400 N 250 NEnergy max. 120 J 105 J Power max. 3900 W 549 W

In addition to a near halving of the necessary static joining force Fand a reduction in the necessary inputted ultrasonic energy incombination with approximately equal amplitude A, the power to beexpended for the entire ultrasonic welding operation was able to besignificantly reduced.

Table 2 shows a comparison of the tensile force for the removal of awelded-on plastic closure devices according to the prior art and aninventive plastic closure device 1 or the bottom part 2, with the use ofthree energy-introducing ribs 23. The above-described bottom parts withidentical surface areas of the flange bottom sides, after having beenfastened on an identical plastic film 5, were loaded after a while withthe below-specified tensile forces under identical conditions.

TABLE 2 Prior art Invention Tensile force (N) 92.00 144.33 Tensileforce/unit of area (N/mm2) 0.43 0.67

It can clearly be seen that the necessary tensile force or tensile forceper unit of area for the detachment of the bottom parts, in the case ofthe bottom part 2 provided with the new energy-introducing arrangement,lies significantly above the comparison value of the traditional bottompart.

As has been explained above, the present configuration of the bottompart 2 was able to bring about an improvement in the previously knownwelding methods, so that an energy-efficient, integral connection ofbottom parts 2 of plastic closure devices 1 with plastic films 5 oftubular bags can be achieved, which connection additionally ensures astill stronger and more resistant connection between the bottom part 2and the tubular bag.

In order to enhance the welded joint, a situation in which the bottomside 200, in the outer marginal region Y of the flange 20, comes intocontact with the plastic film 5 during welding should be avoided. Inorder to prevent a part of the energy from being introduced into theplastic film 5 outside the desired joining zone Z during the weldingoperation, the bearing of the bottom side in the marginal region Y ofthe flange 20 is avoided by virtue of the fact that bottom side 200 isguided after the outer energy-introducing rib 23 in the direction of theflange top side 201. This is illustrated in FIG. 5 a. The stronglyrounded marginal region Y of the flange 20 is distinguished by the factthat the bottom side 200 merges into the flange top side 201, whereinthe distance of the bottom side 200 to the plastic film 5 corresponds tothe height h of the energy-introducing rib 23 only directly at the outerenergy-introducing rib 23. As a result of the bottom side 200 in themarginal region Y, said bottom side being curved away from the plasticfilm 5, the welding energy remains limited to the joining zone Z andthus no adhesion of the plastic film 5 occurs beneath the marginalregion Y of the flange 20. As a result of this concentration of weldingenergy, the necessary energy can be additionally reduced.

In FIG. 5 b, a section through the flange 20 along the sectional lineW-W according to FIG. 2 is represented. Here too, the bottom side 200 iscurved after the outer, in this case second energy-introducing rib 23strongly away from the plastic film 5 in the direction of the flange topside 201, whereby the resulting marginal region Y after the outerenergy-introducing rib 23 is strongly curved and is distanced from theplastic film 5. That surface area of the flange bottom side 200 whichlies opposite the plastic film 5 is thus minimized, whereby almost nowelding is performed in this marginal region Y. The introduced energy isthus concentrated on the energy-introducing ribs 23.

1. A plastic closure device for tubular bags, having a bottom part (2),comprising a discharge outlet (22) and a flange (20) having a flangebottom side (200) on which there is disposed an energy-introducingarrangement which can be connected to a plastic layer by ultrasonicwelding, characterized in that the energy-introducing arrangementcomprises at least two energy-introducing ribs (23), which runapproximately parallel to one another along the flange bottom side (200)and respectively project away from the flange bottom side (200) by aheight (h).
 2. The plastic closure device (1) as claimed in claim 1,characterized in that the energy-introducing ribs (23) are arranged overa width (b) of about 2.5 to 2.7 mm which is less than or equal to thewidth of a bearing edge (61) of a sonotrode (6).
 3. The plastic closuredevice (1) as claimed in claim 2, characterized in that a flange topside (201), above the region in which the energy-introducing ribs (23)are arranged (b), is freely accessible.
 4. The plastic closure device(1) as claimed in claim 1, characterized in that respectively adjacentenergy-introducing ribs (23) are arranged at a distance apart (b′) of 1to 1.5 mm.
 5. The plastic closure device (1) as claimed in claim 1,characterized in that energy-introducing ribs (23), at theircircumferential domes, are configured rounded with a radius (r) of 0.1to 0.3 mm in cross section.
 6. The plastic closure device (1) as claimedin claim 1, characterized in that flanks of the energy-introducing ribs(23), which flanks are visible in cross section, enclose an angle (α) of50° to 70°.
 7. The plastic closure device (1) as claimed in claim 1,characterized in that domes of the energy-introducing ribs (23) areconfigured to form, viewed in cross section, roughly punctiform bearingsurfaces of the energy-introducing ribs (23).
 8. The plastic closuredevice (1) as claimed in claim 1, characterized in that the height (h)of the energy-introducing ribs (23) is between 0.2 and 0.4 mm.
 9. Theplastic closure device (1) as claimed in claim 1, characterized in thatthe bottom side (200), in a marginal region (Y) adjoining an outerenergy-introducing rib (23), is curved in a direction of a flange topside (201).
 10. The plastic closure device (1) as claimed in claim 1,characterized in that the energy-introducing arrangement comprises threeenergy-introducing ribs (23).
 11. The plastic closure device (1) asclaimed in claim 1, characterized in that respectively adjacentenergy-introducing ribs (23) are arranged at a distance apart (b′) of1.25 mm.
 12. The plastic closure device (1) as claimed in claim 1,characterized in that flanks of the energy-introducing ribs (23), whichflanks are visible in cross section, enclose an angle (α) of 60°. 13.The plastic closure device (1) as claimed in claim 1, characterized inthat the height (h) of the energy-introducing ribs (23) is 0.3 mm.